81645560 has 32 divisors (see below), whose sum is σ = 194510160. Its totient is φ = 30736896.

The previous prime is 81645547. The next prime is 81645563. The reversal of 81645560 is 6554618.

81645560 = T₁₀₉ + T₁₁₀ + ... + T₇₈₈.

It is a happy number.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 81645560.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81645563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59354 + ... + 60713.

Almost surely, 2^81645560 is an apocalyptic number.

It is an amenable number.

81645560 is an abundant number, since it is smaller than the sum of its proper divisors (112864600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81645560 is a wasteful number, since it uses less digits than its factorization.

81645560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120095 (or 120091 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 35.

The square root of 81645560 is about 9035.7932689942. The cubic root of 81645560 is about 433.8212859718.

The spelling of 81645560 in words is "eighty-one million, six hundred forty-five thousand, five hundred sixty".